1. Field of the Invention
The present invention relates to the field of reconditioning machine parts, particularly automotive parts.
2. Description of the Backcround Art
Most automobiles manufactured in the world today utilize rack and pinion steering systems. In recent years, hydraulic power assist has been added to rack and pinion steering systems which utilize a control valve assembly and a hydraulic cylinder thereof attached directly to the rack. With hydraulic power assist, hydraulic pressure is applied to one side or the other of the rack piston proportional to the movement of the steering column so as to move the rack in the desired direction and thereby steer the vehicle.
In rack and pinion steering systems with hydraulic power assist, the rack piston is sealed against the hydraulic cylinder with a face seal. The rack shaft, which transmits the force of the piston to the tie rods, serves as a seal face at opposite ends of the hydraulic cylinder. All of these seals are subject to wear due to the nature of the finish of the rack shaft and the cylinder surfaces. When the seals begin to leak, protective boots extending between the tie rods and the ends of the cylinder, which protect the ends of the cylinder from contact with contaminants and debris, begin to fill with hydraulic fluid. Output from the hydraulic pump of the power assist system can thereby be reduced or interrupted and malfunctions may occur.
The natural progression of wear on rack and pinion systems can be accelerated by the introduction of foreign matter in the hydraulic reservoir, or by puncture or failure of one or both of the protective boots, thereby exposing the ends of the hydraulic cylinder. Once this occurs, the progression of malfunction is accelerated when the rack shaft and/or cylinder bore becomes pitted or scored, and leakage becomes a major problem. Similar problems can occur within the pinion housing, causing wear of bearing surfaces therein.
There are various known methods for reconditioning or refurbishing worn machine parts. For example, U.S. Pat. No. 4,724,819 to Fleri discloses a cylinder liner reconditioning process wherein the internal wall of a cylinder liner is cleaned and grit-blasted. A bond coat then is applied to the cylinder wall, followed by steel coating and then coating with Teflon. The thus coated liner then is placed in an oven so as to permanently bond the Teflon thereto.
Other methods for reconditioning machine parts are disclosed in U.S. Pat. Nos. 1,658,173, 3,715,790, 3,728,776, 4,091,518 and 4,292,723, as well as Soviet Patent Publication Nos. 564,136 and 98/00105.
Despite the numerous proposals for reconditioning machine parts known in the art, there remains a need for reconditioning processes for machine parts such as those utilized in rack and pinion steering systems.